Teensy: usb_rawhid

#!/usr/bin/env python
##########################################################################################################
#
# Python implementation of the usb_rawhid host-side functions for the Teensy (and other raw HID devices).
# Requires the libhid library.
#
# Craig Heffner
# 21-July-2011
# http://www.devttys0.com
#
##########################################################################################################

import sys
try:
    from hid import *
except Exception, e:
    print e
    print "Please install libhid: http://libhid.alioth.debian.org/"
    sys.exit(1)

class RawHID:

    READ_ENDPOINT = 0x81
    WRITE_ENDPOINT = 0x02
    INTERFACE = 0

    PACKET_LEN = 64
    TIMEOUT = 1000 # milliseconds
    CONNECT_RETRIES = 3

    def __init__(self, verbose=False):
        self.verbose = verbose
        self.hid = None
        return None

    # Initialize libhid and connect to USB device.
    #
    # @vid - Vendor ID of the USB device.
    # @pid - Product ID of the USB device.
    #
    # Returns True on success.
    # Returns False on failure.
    def open(self, vid, pid):
        retval = False

        hid_ret = hid_init()
        if hid_ret == HID_RET_SUCCESS:
            self.hid = hid_new_HIDInterface()
            match = HIDInterfaceMatcher()
            match.vendor_id = vid
            match.product_id = pid

            hid_ret = hid_force_open(self.hid, self.INTERFACE, match, self.CONNECT_RETRIES)
            if hid_ret == HID_RET_SUCCESS:
                retval = True
                if self.verbose:
                    hid_write_identification(sys.stderr, self.hid)

            elif self.verbose:
                sys.stderr.write("hid_force_open() failed with error code: %d\n" % hid_ret);
        elif self.verbose:
            sys.stderr.write("hid_init() failed with error code: %d\n" % hid_ret)

        return retval

    # Close HID connection and clean up.
    #
    # Returns True on success.
    # Returns False on failure.
    def close(self):
        retval = False

        if hid_close(self.hid) == HID_RET_SUCCESS:
            retval = True

        hid_cleanup()

        return retval

    # Send a USB packet to the connected USB device.
    #
    # @packet  - Data, in string format, to send to the USB device.
    # @timeout - Read timeout, in milliseconds. Defaults to TIMEOUT.
    #
    # Returns True on success.
    # Returns False on failure.
    def send(self, packet, timeout=TIMEOUT):
        retval = False

        hid_ret = hid_interrupt_write(self.hid, self.WRITE_ENDPOINT, packet, timeout)

        if hid_ret == HID_RET_SUCCESS:
            retval = True
        elif self.verbose:
            sys.stderr.write("hid_interrupt_write() failed with error code: %d\n" % hid_ret)

        return retval

    # Read data from the connected USB device.
    #
    # @len     - Number of bytes to read. Defaults to PACKET_LEN.
    # @timeout - Read timeout, in milliseconds. Defaults to TIMEOUT.
    #
    # Returns the received bytes on success.
    # Returns None on failure.
    def recv(self, plen=PACKET_LEN, timeout=TIMEOUT):

        hid_ret, packet = hid_interrupt_read(self.hid, self.READ_ENDPOINT, plen, timeout)

        if hid_ret != HID_RET_SUCCESS:
            packet = None
        elif self.verbose:
            sys.stderr.write("hid_interrupt_read() failed with error code: %d\n" % hid_ret)

        return packet



# Example code to interface with the Teensy Raw HID Example firmware
if __name__ == "__main__":

    BYTES_PER_LINE = 16

    # Teensy vendor ID and product ID
    vid = 0x16C0
    pid = 0x0480

    hid = RawHID()

    # Open a connection to the Teensy
    if hid.open(vid, pid):

        print "\nConnected to Teensy..."

        # Turn on the Teensy pins D0-D3
        hid.send("\x0F")

        try:
            # Infinite loop to read data from the Teensy
            while True:
                data = hid.recv(timeout=50)
                if data is not None:
                    size = len(data)
                    print ""
                    print "recv %d bytes:" % size

                    # Print out each hex byte, 16 bytes per line
                    for i in range(0, (size / BYTES_PER_LINE)):
                        for j in range(0, BYTES_PER_LINE):
                            print "%.2X" % ord(data[(i*BYTES_PER_LINE)+j]),
                        print ""
        except KeyboardInterrupt:
            pass

        # Close the Teensy connection
        hid.close()

        print "\nDisconnected from Teensy.\n"
    else:
        print "Failed to open HID device %X:%X" % (vid, pid)